OCR Text |
Show and Y1 - 0.044(TiO2)°-09,t • (Fe203)0-"" • (CaO)0-221 ' (MgO)0-220 • (Na20)°-728 (7) Sodium was found to be the most significant constituent; magnesium was surprisingly high on the list of significant constituents. The role of magnesium, however, appeared to depend upon the presence of CaO and Na20. The utility of the correlation is in its ability to relate ash chemistry directly to operating time between outages. The fouling index has also been used to flag core samples in the mine field to permit blending of the coal to maintain a low sodium level.26 The statistical analysis has served to identify the role of different elements in specific coals on influencing the melting temperature of the ash. When applied to rank coal, they take into consideration some variations in mineral content. When applied to size- and gravity-fractionated coal, the mineral distribution illustrates the heterogeneity of the coal. With an exception for Garner's work, the correlations do not directly predict fouling or slagging. They qualitatively imply potentials for slagging and massive fouling if furnace exits are improperly selected. In low-rank coals in particular, they do not relate to the initial ash deposition in either the convection pass or furnace. The correlations do not account for mineral content variation and distribution in the fuel or segregation of ash by elemental composition in the furnace. Including Garner's work, they cannot easily be applied to fuels other than those upon which they were based. 1-28 |